Alexandra Witze writing for Nature:
Fragments of the asteroid Bennu, carefully collected and ferried to Earth by a robotic spacecraft, contain the building blocks for life, NASA announced today.
Not only does Bennu contain all 5 of the nucleobases that form DNA and RNA on Earth and 14 of the 20 amino acids found in known proteins, the asteroid’s amino acids hold a surprise. On Earth, amino acids in living organisms predominantly have a ‘left-handed’ chemical structure. Bennu, however, contains nearly equal amounts of these structures and their ‘right-handed’, mirror-image forms, calling into question scientists’ hypothesis that asteroids similar to this one might have seeded life on Earth.
This is an interesting discovery. The closest I read something similar in fiction was in Dan Brown’s Deception Point where NASA discovers a meteorite filled with fossils.
The discovery also raises a few questions.
Glavin is most perplexed by the discovery of an equal mixture of left-handed and right-handed amino acids on Bennu. He, like many scientists, had thought that organic molecules from primordial asteroids would have had the same left-handed dominance as those from life on Earth. Now, researchers have to go back to the drawing board to understand how life might have been seeded on Earth.
“I felt a little bit disappointed at first, like it invalidated 20 years of my research,” Glavin says. “But this is why we explore — to learn new things.”
I tried to understand why amino acids are left handed, but that was too heavy for me to understand.